1. Field of the Invention
The present invention relates to an improved method for depolymerization of cyclic trimers of aliphatic aldehydes with the chlorinated 2-position (hereinafter referred to as chloroaldehyde) which is useful as a raw material for synthesis of organic chemicals.
2. Description of the Background Art
Chloroaldehydes having the chlorinated 2-position, such as monochloroacetaldehyde (hereinafter referred to as MCA) and 2-chloropropionaldehyde (hereinafter referred to as CPA), are useful compounds as raw materials for the synthesis of drugs, agricultural chemicals, and polymers. Because these are extremely unstable compounds, MCA is sold as an aqueous solution with a concentration of approximately 40% and CPA is not commercially available. Japanese Patent Laid-open (Kokai) Nos. 223575/1990 and 173785/1992 therefore propose to store these chloroaldehydes in a stable manner as cyclic trimers and obtain MCA or CPA by depolymerizing the trimers upon use.
The method disclosed by these Japanese Patent Laid-open specifications comprises depolymerizing the chloroaldehyde cyclic trimers using a catalyst such as p-toluenesulfonic acid or sulfuric acid at 120.degree.-130.degree. C. in the absence of a solvent. However, the depolymerization of these trimers using p-toluenesulfonic acid or sulfuric acid as a catalyst in the absence of a solvent involves various side reactions of monomers produced, causing production of high boiling point components. Because of this, it is essential to separate the products by distillation after the depolymerization reaction. Carbonated residues obtained by the distillation must be appropriately treated and washed, which makes it difficult for the catalyst to be recycled for reuse.